Side Bumpers Look Odd, But Could Increase Safety

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Side Bumpers Look Odd, But Could Increase Safety

A Boston-area inventor is developing an unusual system of side bumpers and crumple boxes to make stronger small cars, something he says will make fuel-efficient compact vehicles more attractive to safety-conscious buyers.

Compacts and subcompacts have grown increasingly safe over the years as manufacturers have installed multiple airbags and other features while also reinforcing the doors for side-impact collisions. But the added technologies carry a weight penalty, which is why a car like the 1987 Chevrolet Sprint got Prius-worthy mileage even without the battery behind the back seat.

Steve Shoap is eager to encourage automakers to put their cars on a weight-loss program that would help increase fuel efficiency – thereby cutting CO2 emissions. So the MIT grad recently patented a safety system he says will allow manufacturers to build smaller, lighter cars without compromising occupant safety. The Safer Small Cars system uses collapsible side bumpers that absorb the force of an impact.

They work a lot like the bumpers on the front and back of the car in your driveway, but they can take the brunt of a side impact. They're connected to a compartment of energy absorbing material that Shoap calls a crumple box. In the event of an impact, the bumpers collapse into the crumple box, absorbing the impact force. Rather than reinforcing the doors and B-pillars – the vertical supports often found between the front and rear doors of a sedan – Shoap says a small car car built using his safety system could be lighter, and therefore more fuel-efficient.

"My side bumpers allow B-pillars to be much lower cost," he said. "Car doors can be made much thinner and lighter."

So far Shoap has only built a two-foot prototype (shown above) that looks like a Tonka version of the Volkswagen Thing, but he's looking to catch the eye of major automakers and parts suppliers. The University of Dayton Design and Manufacturing Clinic is working with him to refine the design and put together some cost estimates for producing it. Shoap says the material costs for a crumple box and rear bumper would be $1,300 with another $640 for bumpers on each side.

Shoap says a detailed analysis from the Dayton team proves the impact-absorbing bumper brackets would not penetrate the passenger compartment in a collision. Rather, they'd either collapse into the crumple box or bend upward.

The prototype pictured above looks a little, well, ugly. But Shoap says it would be designed into production cars. He thinks it would look best as part of a package with fenders and running boards like, say, an old VW Beetle, which he says also would help people judge the width of their cars when parking. Fenders and running boards aren't terribly aerodynamic, and aerodynamics are of course a key part of fuel efficiency. But Shoap says the aerodynamic penalty would be more than offset by the reduced size and weight of the vehicle.

Shoap also developed exterior crumple boxes for retrofit. With a weight penalty of 300 pounds for a manually extending rear bumper and an estimated cost of $1,700 installed, the system just might revive interest in that '87 Chevy Sprint.

We tried to get some second opinions from automotive engineers on how well such a system might work and whether it's been tried, but apparently it's as novel as Shoap says. Those that got back to us let us know they didn't know enough about side bumpers to comment on them. The rest of them didn't get back to us.